TDI image sensor may realize higher SNR and sensitivity due to its special scanning manner and is especially suitable for high speed movement and low illumination environment. The basic principles of TDI lie in linear scanning with area pixel matrix, thus realizing exposure of the same moving object by pixels of different lines, and accumulating of exposure result of each time. This equivalently extends exposure integration time of the object, thereby greatly improving SNR and sensitivity. The conventional TDI image sensors are formed by CCD devices. Compared to CCD image sensor, CMOS image sensor has lower power consumption, lower cost, and higher integration. As such, in case the TDI function (CMOS-TDI image sensor) is realized by CMOS image sensor, cost of the TDI camera will be decreased dramatically and it will be widely used. In prior art, to realize TDI function using CMOS image sensor, analog signal accumulators are incorporated into the CMOS image sensor to work as a CMOS-TDI image sensor. That is, analog signals output by the pixels are in advance input into the analog signal accumulator to finish accumulation of the identically exposed signals, and then accumulated analog signals are sent to the ADC to be output quantitatively. Furthermore, prior art has also proposed to quantitatively output signals of the CMOS image sensor through the ADC at first and then, finish accumulation of identically exposed signals by a digital domain accumulator built in chip. These two kinds of techniques, either performing accumulation and then quantitative output or performing quantification and then accumulative output, both require reading out of exposure result of all pixels of the CMOS image sensor during a single exposure period (that is line transfer period). As a result, readout speed certainly will limit the shortest exposure period, i.e., the largest scanning frequency. To solve this problem, prior art has proposed integration of buffer cell into the pixels to realize signal delivery between adjacent pixels. Similar to CCD-type TDI image sensor capable of realizing accumulation of signals in a pipelined manner, only the output of the last line of pixels during each exposure time needs to be read out quantitatively. Accordingly, limitation of the scanning frequency caused by readout speed is eliminated, thereby realizing faster scanning frequency. This technique however, during pipelined accumulation of pixel output signal, will introduce a great deal of thermal noise and offset voltage of the operational amplifier. In addition, fill factor of pixels is decreased due to integration of buffer cells into the pixels, hence limiting sensitivity of the sensor.